Your problem probably is that you haven‘t installed python. Meaning that, if you are using Windows, you have not downloaded the installer for Windows, that you can find on the official Python website.
In case you have, chances are that PyCharm cannot find your Python installation because its not in the default location, which is usually C:\Python27 or C:\Python33 (for me at least).
So, if you have installed Python and it still gives this error, then there can be two things that have happened:
virtualenv and that virtualenv has been deleted or the filepath changed. In this case, you will have to find proceed to the next part of this answer.python.exe file.Once you have located the necessary binaries, you will need to tell PyCharm were to look:
Then you will need to type in interpreter in the search box:
As you can see above, you will need to go to Project Interpreter and then go to Python Interpreter. The location has been selected for you in the above image.
To the side you will see a couple of options as icons, click the big + icon, then click on local, because your interpreter is on this computer.
This will open up a dialogue box. Make sure to select the python.exe file of that directory, do not give pycharm the whole directory. It just wants the interpreter.
原文在：http://stackoverflow.com/questions/19645527/trying-to-get-pycharm-to-work-keep-getting-no-python-interpreter-selected
转载的，刚装完 PyCharm , 却遇到“No Python interpreter selected”该怎么办
原文：http://www.cnblogs.com/AimeeKing/p/4853999.html